Okay, I haven't even attempted to make a "serious" team yet, since the meta is a madhouse and is probably going to take another month or two to really settle down between bans, people moving past new toy syndrome to settle on what actually works, and whatever decision is made with Tera. I've been exclusively laddering on my meme account, mostly testing out second tier mons and off-meta sets and sticking in the high 1400s across a bunch of styles. So, here are a bunch of thoughts from a truly mediocre player:
Gholdengo/Glimmora cores rarely seem as effective in practice as they do on paper. Glimmora just isn't that great at setting up hazards beyond TSpikes, and even then, the activation order with toxic debris rapid spin really hurts it. I honestly think Rocky Helmet Endure Glimmora is a decent set to create more opportunities later in the match to get up multiple layers of Tspikes while possibly messing with Rapid Spinners. But, really, that's mostly a good reminder that Garchomp might be the best hazard setter in the tier. Vastly bulkier, and that helmet+rough skin chip adds up quick and functionally blocks spins from weakened `mons. Clodsire and even Gastrodon are pretty fire, too, for more defensively minded teams. Gastro getting spikes and rocks is legit huge.
As for Gholdengo in particular, its defog immunity is really just icing on the cake, since using it to protect hazards just invites it to die to knock -> EQ from either new Donphan form. The overall status immunity, and the fact that it includes things like taunt, disable, and leech seed, is huge. I get the appeal of Scarf sets, but bulky Air Balloon has my heart when I stoop to using it.
On the topic of status immunity, Garganacl is a fantastic example of a mon that is really made by Tera without feeling dirty. Being able to grab momentum by freely switching into a predicted Spore/Wisp/whatever is amazing, but Rock is just not a good defensive type. Being able to tech into a Flying or Ghost or whatever best fits your team, along with the amazingness of Salt Cure and Purifying Salt, makes it a tier staple instead of an oddity (though the lack of good waters and grasses might keep it OU pre-home even without Tera). Skeledirge is another `mon that fits the bill here. It's probably UU without Tera, but with Tera it has an obvious role as defensive glue, even with more broken abusers around.
It's kinda nuts that the starter with protean feels the least reliable, but Meowscarada struggles so much with the speed/power creep (and the Protean nerf). It really wants to run Band for the extra oomph, but then you're at the mercy of `Pult, Scarf Gholdengo, Energy Booster Iron Valiant and more. Some of those faster `mons can be handled by Sucker Punch, but you need to have scouted the set first, and you lose a ton of momentum if they predict it. Scarf sets are...fine? Protean U-Turn will always have its uses. Quaquaval, meanwhile, doesn't remotely fill the niche Palafin vacated, but it's something you can't allow to start rolling.
I feel bad for besmirching the name of Lokix many pages ago. It is one last "balanced" tera abuser I'd like to call out, this time on the pseudo-Adaptability front. Tinted Lens First Impression is just stupid and helps keep so much otherwise unmanageable stuff in check. I'm a big big fan of the Silver Powder set I mentioned way back with FI/U-Turn/Sucker/Taunt. FI -> Taunt -> U-Turn on bulkier switch-ins (or Sucker Punch if they're in range) is just such a nice sequence to have in your pocket that it's worth giving up the extra juice you get from Band.
I'm very happy for Kilowattrel that Pelipper dropped to UU for now. I wanted to love bargain-bin Zapdos so bad, but it has a hard time outside of rain, and it's so frail that it's super unreliable there. Gholdengo also made it hard for it to run Competitive in OU to get the power boost it needs, though Water Tera with Volt Absorb is probably its best set for as long as Tera is around.
I've mentioned Tera a lot, and I find that I really enjoy it. It makes the whole meta a bit fishier overall, but I never eyeroll at it the same way I did Dynamax because it's not just "oh, great, now there's a super-mon on the field and I didn't bring my Ditto". There are definitely a bunch of `mons that you look at and think "well, I'm screwed if that thing gets position", but I'd much rather see some combination of the biggest offenders, Shed Tail, and Light Clay go before Tera at this moment to make people have to work harder to maneuver into those spots.
One final lightning round of new `mons/sets I've really enjoyed playing with.
Sub/Disable/Wisp/Hex Dragapult gets work done. It's not as blunt an instrument as Specs/Band, but it also means you never have to worry about Annihilape or any Specs/Band set ever, and rarely needs a Tera boost to get its work done.
Iron Hands is fantastic. Every match, it at least eats a big hit to get something I couldn't otherwise handle into revenge-able range. It is best friends with Lokix in this way.
Baxcalibur feels like what I always wanted Tyranitar to be, if that makes sense. After a DD, it just takes names. I've had it run through the last 3 `mons on the opposing team to steal a win multiple times.
Iron Moth is definitely best run with Agility but then it has severe 4MSS. It also wishes it could run Boots and LO at the same time, but if it gets lucky with a Fiery Dance boost or two, watch out.
I swear to god scarf Flamigo has a niche in OU as the fastest (non-mega) Scrappy Fighting type we've ever had. It somehow doesn't even need a fourth move beyond CC+BB+U-turn, though it wishes Scarf Chi-Yu and Iron Valiant didn't exist.
Aaaand, that's all. Hopefully some helpful thoughts there for someone. Anything anybody else is enjoying playing with?